TDR fill level measurement devices comprise coaxial probes which substantially consist of an external conductor and an internal conductor arranged concentrically therein. This elongate probe is immersed into the filling material, and a measurement signal is sent through the probe towards the filling material from the measurement electronics attached to the upper end of the coaxial probe. This measurement signal is reflected in particular at the filling material surface, and is returned to the top along the coaxial probe until it is then received by the measurement electronics.
The internal conductor is held and fixed by spacers so as to be spaced apart from the external conductor.
Each of the spacers causes both a transit time offset of the measurement signal, which leads to an offset between the measured value and the filling material surface, and a reflection of the transmission signal, which can impair the measurement accuracy.